rim and tire set up PLEASE HELP

I know this has been talked about but all i could find was a couple years ago that it was. I just bought a 2014 stealth black rzr 900 xp only 4 hours , almost like new. I live in georgia and will be riding a large trail on some private land, little sandy . loamy mixed with GA clay. not looking for any DEEP MUDDING, been there done that with 4 wheels to much breaks, will not be doing any ROCK climbing. but i like to ride fast and a bit hard?
i am thinking going to 14 inch rims, but what width rim? should i make all 4 the same ? and what size tires? i dont want to hurt top speed or take off?
I am sure it has been figured out to a science by now. so any info or thoughts would be VERY HELPFULL.